<!DOCTYPE html>
<!-- Form with one invalid element and a barred for constraint validation element -->
<html>
  <head>
    <style>
      form:invalid { display: none; }
    </style>
  </head>
 <body>
   <form>
    <input id='i' value='bar'required>
    <input id='i' value='foo' readonly required>
   </form>
 </body>
</html>
